A Microsoft technology for creating dynamic websites, such as sites linked to databases. ASP provides a form of server-side scripting - programs running on a web server which can generate web pages on-the-fly, in response to user requests. ASP is normally used in conjunction with IIS, the Microsoft web server product. ASP has now been superseded by ASP.NET.
US MIL HANDBOOK 217E
CNET (French PTT) Data
HRD5 (British Telecom)
RADC Non-Electronic Parts Handbook NPRD
OREDA (Offshore data).
The proportion of time that an item is capable of operating to specification within a large time interval.
This is the distribution of the standard deviation determined from a normal population. It arises in the calculation of the rate of occurrence from truncated life tests.
Decisions that can be expressed as a real numbers representing a quantity that selected in smoothly rather than in steps.
The action of replacing a failed item in a product or system. The maintenance action should include logistic, diagnostic and restart actions needed to bring the equipment fully back on line, unless some of these activities are considered elsewhere.
A function that returns a value from a well ordered set for each of the outcomes from a set of decisions. The well ordered set is usually the set of all real number and the cost can often be interpreted in monetary terms.
Defined and used in MIL-STD-498 to provide descriptions of document deliverables for software projects. A DID specifies the chapters and outlines the required chapter contents for the document deliverable. MIL-STD-498 supplies a comprehensive set of DIDs which may be used by an organisation as a starting point in developing their own set of DID.
A software system which stores information in a structured format, so that it can be easily indexed and retrieved. A small personal database, such as an address list, can run on a user’s workstation. Larger databases which are used by numbers of users are normally run on a separate server, and are accessed over a network.
Decisions in which the alternatives are individually distinct. Examples are decisions which are the number of individual items (machines in a factory), an quantity that can be enumerated (machine type) and particularly yes/no decisions.
A series of standards covering the application of electronic products for uses with safety aspects in railways. Covers both hardware and software aspects.
The end of the period ot time when an item can perfrom its required function or maintain a specified level of performance. Failures can be categorised by cause and type.
The functional consequence of a specific failure. Failure of an item may not result in the loss of all functions performed by the item.
The number of failures of an item per unit time. May be observed failure rate (e.g. from 'returns' data); assessed failure rate (from tests) or extrapolated (from tests at higher stress levels).
A graphical method of modelling the reliability of the system as AND and OR gates and failure events.
Microsoft’s web server (software) product. In addition to serving websites, IIS provides a platform for Web Applications, and includes suite of other Internet services: a FTP [File Transfer Protocol] service for large file uploads and downloads, a limited email service for web-email integration, a Network News discussion group service, and a Web Folders service (for sharing files over the web).
A set of decisions that are mutually incompatible. For example if the decisions are the quantities of different products to manufacture in the next week, a set of these decisions (one value for each product) will be incompatible if the total time required on a particular machine exceeds what is available.
Independent failure is when items do not fail by a common cause, but fail through random normally unknown causes.
Maintenance activities for a large organisation are usually organised into levels.
First level maintenance uses relatively unskilled labour and covers cleaning,
inspections and other simple preventative maintenance activities.
Second level maintenance involves the diagnosis of faults and replacement of failed modules.
Third level maintenance is usually outsourced and repairs failed modules.
A simplified description providing a basis for an empirical understanding and representation of a system that can be used to forecast its behaviour according to a set of decisions.
A collection of hardware components that are more or less permanently connected. If a component in the module fails the complete module is replaced.
The mean time between failures is the total time divided by the total number of failures. When the failure rate is constant with respect to time MTBF is the reciprocal of the failure rate.
The mean time to restore service is the total repair time divided by the total number of repairs (failures). The repair rate is usually constant with respect to time so that MTTRS is the reciprocal of the repair rate. The repair action should include logistic allowance, diagnosis time, and time needed to bring the equipment fully back on line, unless some of these activities are considered elsewhere.
making a set of decisions that provides the best outcome (minimum value) according to a cost function.
A statistical distribution that gives the probability of obtaining exactly n successes in N when the probability of obtaining a successful trial is low. It is the limiting case of the Binomial distribution when the probability is low.
A quality management system is the set of interrelated or interacting elements that direct and control an organisation with regard to quality.
Document that demonstrates the compliance of an organisation with ISO 9001:2000. Should contain sections dealing with: scope and exclusions; documented procedures and interactions between processes.
The quality plan should document the quality activities for each software development on the basis of the quality organisation. A quality plan should be developed or identified for each software project.
The probability that an item will perform a required function under stated conditions for a stated period of time. Reliability is an extension of quality into the time domain and may be considered informally as the probability of non-failure in a given period or the ratio of items which perform their function for the stated period to the total number in the sample.
Unfortunately due to the uncertainty in the data available, agreement on the period of time and no role for maintenance this definition often provides little useful information. Informally reliability is often confounded with the term availability, which is related to the average probability that the item will be functioning at some instant in the future.
A diagram that links the elements of a product that need to be working for the product to work. So long as there is a path from the start of the diagram to the end of the diagram the equipment can provide the service. The diagrams can be hierarchical so that blocks at one level can be decomposed into an RBD at a lower level.
A simplified description of a system or product that represents reliability performance. The main types of reliability model are reliability block diagrams and fault trees.
The number of corrective maintenance actions that can be carried out in unit time. Corrective action should also include logistic allowance, diagnosis time, and time needed to bring the equipment fully back on line, unless some of these activities are considered elsewhere in calculations.
Failures that are immediately recognised, possibly by some monitoring system. The alternative is that the failure of modules may only be revealed during regular inspections. Unrevealed failures result in less protection by redundancy since on average the item will be unavailable for half the inspection period for each failure.
A box and arrow diagram based method. While SADT is a trademarked and copyrighted by Softech Inc. the term SADT is often used for any box and arrow method using complementary data flow and functional viewpoints. The structured element is often introduced by ensuring that individual diagrams have no more than six boxes so that a hierarchical structure is enforced. SADT diagrams are easily understood by non-specialists. SADT tends to lead to a functionally based design.
The method by which new consistent decision set can be identified in such a manner that eventually the 'best' decision set will be found.
A measure of the safety consequences resulting from failure of a product, system or sub-system. Ranges from 0 (no safety consequences) to 4 (safety critical). Assessed by taking into account the likely hood of failures causing injuries and the likely severity of injuries sustained.
A model of a system on a computer that includes events that represent the progress of the system towards the final state. At each event choices are made and forthcoming events are registered. The model can deal with uncertainty by triggering events according to random distributions. By running the model for long enough (or enough times) the average results from the model will provide a forecast of 'typical' behaviour. Simulations are used to deal with both uncertainty and complexity.
A popular acronym for small-to-medium sized commercial enterprises. The EU currently defines “small” as up to 50 employees, and “medium” as up to 250 employees.
Carried out by examination of code and checking the code for errors prior to actually running the code. Static testing should be carried out as a formal exercise and is facilitated by having coding standards against which the code can be tested.
Two blocks or elements are statistically independent if knowing that one of them has failed makes it neither more probable nor less probable that the other block has failed. If blocks are not statistically independent then conditional probabilities have to be used to calculate the overall probability of failure of service.
The propourtion of time that an item is incapable of operating to specification within a large time interval. Equals 1 - Availability.
A requirements capture method that identifies the 'users' of the system and the actions (cases) that the system should support. The 'users' of the system are frequently human but may be external systems. Use Cases concentrates entirely on capturing high-level, user-centric requirements and leads naturally into object oriented design techniques.
The part of a software application which the user can see and interact with. If software was a car, then its user interface would be the steering wheel, pedals, instrument panel and so on.
The process of evaluating software to ensure that it meets the customers requirements.
The process of ascertaining (by test and or analysis) that a development stage has been completed satisfactorily.
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